[PATCH v3 2/2] fpga: dfl: look for vendor specific capability

From: matthew.gerlach@linux.intel.com
To: linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org,
	mdf@kernel.org, hao.wu@intel.com, trix@redhat.com,
	linux-doc@vger.kernel.org, corbet@lwn.net
Cc: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Subject: [PATCH v3 2/2] fpga: dfl: look for vendor specific capability
Date: Tue, 24 Nov 2020 07:56:58 -0800	[thread overview]
Message-ID: <20201124155658.700976-3-matthew.gerlach@linux.intel.com> (raw)
In-Reply-To: <20201124155658.700976-1-matthew.gerlach@linux.intel.com>

From: Matthew Gerlach <matthew.gerlach@linux.intel.com>

A DFL may not begin at offset 0 of BAR 0.  A PCIe vendor
specific capability can be used to specify the start of a
number of DFLs.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
---
v3: Add text and ascii art to documentation.
    Ensure not to exceed PCIe config space in loop.

v2: Update documentation for clarity.
    Clean up  macro names.
    Use GENMASK.
    Removed spurious blank lines.
    Changed some calls from dev_info to dev_dbg.
    Specifically check for VSEC not found, -ENODEV.
    Ensure correct pci vendor id.
    Remove check for page alignment.
    Rename find_dfl_in_cfg to find_dfls_by_vsec.
    Initialize target memory of pci_read_config_dword to invalid values before use.
---
 Documentation/fpga/dfl.rst | 25 +++++++++++
 drivers/fpga/dfl-pci.c     | 91 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 115 insertions(+), 1 deletion(-)

diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
index 0404fe6ffc74..fa0da884a818 100644
--- a/Documentation/fpga/dfl.rst
+++ b/Documentation/fpga/dfl.rst
@@ -501,6 +501,31 @@ Developer only needs to provide a sub feature driver with matched feature id.
 FME Partial Reconfiguration Sub Feature driver (see drivers/fpga/dfl-fme-pr.c)
 could be a reference.
 
+Location of DFLs on a PCI Device
+===========================
+There are two ways of locating DFLs on a PCI Device.  The original
+method assumed the start of the first DFL to offset 0 of bar 0.
+If the first node of the DFL is an FME, then further DFLs
+in the port(s) are specified in FME header registers.
+Alternatively, a vendor specific capability structure can be used to
+specify the location of all the DFLs on the device, providing flexibility
+for the type of starting node in the DFL.  Intel has reserved the
+VSEC ID of 0x43 for this purpose.  The vendor specific
+data begins with a 4 byte vendor specific register for the number of DFLs followed 4 byte
+Offset/BIR vendor specific registers for each DFL. Bits 2:0 of Offset/BIR register
+indicates the BAR, and bits 31:3 form the 8 byte aligned offset where bits 2:0 are
+zero.
+
+        +----------------------------+
+        |31     Number of DFLS      0|
+        +----------------------------+
+        |31     Offset     3|2 BIR  0|
+        +----------------------------+
+                      . . .
+        +----------------------------+
+        |31     Offset     3|2 BIR  0|
+        +----------------------------+
+
 
 Open discussion
 ===============
diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c
index b27fae045536..a58bf4299d6b 100644
--- a/drivers/fpga/dfl-pci.c
+++ b/drivers/fpga/dfl-pci.c
@@ -27,6 +27,14 @@
 #define DRV_VERSION	"0.8"
 #define DRV_NAME	"dfl-pci"
 
+#define PCI_VSEC_ID_INTEL_DFLS 0x43
+
+#define PCI_VNDR_DFLS_CNT 8
+#define PCI_VNDR_DFLS_RES 0x0c
+
+#define PCI_VNDR_DFLS_RES_BAR_MASK GENMASK(2, 0)
+#define PCI_VNDR_DFLS_RES_OFF_MASK GENMASK(31, 3)
+
 struct cci_drvdata {
 	struct dfl_fpga_cdev *cdev;	/* container device */
 };
@@ -119,6 +127,84 @@ static int *cci_pci_create_irq_table(struct pci_dev *pcidev, unsigned int nvec)
 	return table;
 }
 
+static int find_dfls_by_vsec(struct pci_dev *pcidev, struct dfl_fpga_enum_info *info)
+{
+	u32 bar, offset, vndr_hdr, dfl_cnt, dfl_res;
+	int dfl_res_off, i, voff = 0;
+	resource_size_t start, len;
+
+	if (pcidev->vendor != PCI_VENDOR_ID_INTEL)
+		return -ENODEV;
+
+	while ((voff = pci_find_next_ext_capability(pcidev, voff, PCI_EXT_CAP_ID_VNDR))) {
+		vndr_hdr = 0;
+		pci_read_config_dword(pcidev, voff + PCI_VNDR_HEADER, &vndr_hdr);
+
+		dev_dbg(&pcidev->dev,
+			"vendor-specific capability id 0x%x, rev 0x%x len 0x%x\n",
+			PCI_VNDR_HEADER_ID(vndr_hdr),
+			PCI_VNDR_HEADER_REV(vndr_hdr),
+			PCI_VNDR_HEADER_LEN(vndr_hdr));
+
+		if (PCI_VNDR_HEADER_ID(vndr_hdr) == PCI_VSEC_ID_INTEL_DFLS)
+			break;
+	}
+
+	if (!voff) {
+		dev_dbg(&pcidev->dev, "%s no VSEC found\n", __func__);
+		return -ENODEV;
+	}
+
+	dfl_cnt = 0;
+	pci_read_config_dword(pcidev, voff + PCI_VNDR_DFLS_CNT, &dfl_cnt);
+	dev_dbg(&pcidev->dev, "dfl_cnt %d\n", dfl_cnt);
+	for (i = 0; i < dfl_cnt; i++) {
+		dfl_res_off = voff + PCI_VNDR_DFLS_RES +
+				      (i * sizeof(dfl_res));
+		if (dfl_res_off >= PCI_CFG_SPACE_EXP_SIZE) {
+			dev_err(&pcidev->dev, "%s offset too big for PCIe config space\n",
+				__func__);
+			return -EINVAL;
+		}
+
+		dfl_res = GENMASK(31, 0);
+		pci_read_config_dword(pcidev, dfl_res_off, &dfl_res);
+
+		dev_dbg(&pcidev->dev, "dfl_res 0x%x\n", dfl_res);
+
+		bar = dfl_res & PCI_VNDR_DFLS_RES_BAR_MASK;
+		if (bar >= PCI_STD_NUM_BARS) {
+			dev_err(&pcidev->dev, "%s bad bar number %d\n",
+				__func__, bar);
+			return -EINVAL;
+		}
+
+		len = pci_resource_len(pcidev, bar);
+		if (len == 0) {
+			dev_err(&pcidev->dev, "%s unmapped bar number %d\n",
+				__func__, bar);
+			return -EINVAL;
+		}
+
+		offset = dfl_res & PCI_VNDR_DFLS_RES_OFF_MASK;
+		if (offset >= len) {
+			dev_err(&pcidev->dev, "%s bad offset %u >= %pa\n",
+				__func__, offset, &len);
+			return -EINVAL;
+		}
+
+		dev_dbg(&pcidev->dev, "%s BAR %d offset 0x%x\n", __func__, bar, offset);
+
+		len -= offset;
+
+		start = pci_resource_start(pcidev, bar) + offset;
+
+		dfl_fpga_enum_info_add_dfl(info, start, len);
+	}
+
+	return 0;
+}
+
 static int find_dfls_by_default(struct pci_dev *pcidev,
 				struct dfl_fpga_enum_info *info)
 {
@@ -220,7 +306,10 @@ static int cci_enumerate_feature_devs(struct pci_dev *pcidev)
 			goto irq_free_exit;
 	}
 
-	ret = find_dfls_by_default(pcidev, info);
+	ret = find_dfls_by_vsec(pcidev, info);
+	if (ret == -ENODEV)
+		ret = find_dfls_by_default(pcidev, info);
+
 	if (ret)
 		goto irq_free_exit;
 
-- 
2.25.2

